Wireless communication technology has proliferated into many types of systems and applications such as automobile electronics applications and systems. A device that supports wireless communication includes a wireless receiver and an antenna. Generally, in a wireless receiver, a high-frequency radio signal from an antenna is firstly converted into a signal with an intermediate frequency (IF signal), and then the IF signal is amplified and inputted to a detector. In the detector, a desired signal process, namely, a detection process in which information included in the radio signal is taken out is performed. In this detection process, the gains of the radio signal and the IF signal are set according to signal strength of the electric wave received by the wireless receiver, so as to be in a range in which the detection process can be desirably performed. The signal strength of an electric or magnetic wave is generally referred to as a received signal strength indicator (RSSI), and measured by an RSSI circuit system.
Keyless entry systems are becoming increasingly prevalent at least in the automobile industry. A keyless entry system primarily includes a base station and a key fob. The base station communicates with the key fob wirelessly. Security codes are employed to prevent unauthorized communication as for example, a base station will respond to requests only from a keyless entry key programmed to be associated with that particular base station. With keyless entry system, a mechanical key to open doors, for example, is not needed. The key typically includes a few buttons that are preprogrammed or can be programmed to send a preprogrammed set of instructions to the base station to perform specific operations. For example, a button may be programmed to lock or unlock automobile doors or start the engine.
The keyless entry systems key typically includes a base station that communicates with the key fob. The key fob includes an electronic circuit that sends and receives communication signals to/from the base station that is located inside the automobile. The term automobile is used generally. The description provided in this document may equally apply to other types of machines as well. The base station is programmed to communicate with the control systems of the automobile to effectuate performance of requests received from the key fob.
In a keyless or passive key system based automobile, typically the key simply need to be inside the automobile in order for a user of the automobile to operate the automobile. The key detection within the automobile compartment is typically performed through RSSI measurements. Therefore, it is necessary that RSSI measurements are performed accurately.